1. Field of the Invention
The field of this invention lies within the heat exchanger art. It includes the field of boiler economizers or recovery units that are utilized with boilers, to save energy from exhaust gases.
2. The Prior Art
The prior art related to economizers and heat exchangers including boilers encompasses a broad spectrum. It includes economizers for providing heated gas for utilization within the burning process of a boiler, as well as heated fluids that are later to be expanded. In other words, the prior art encompasses not only the concept of using the residual or remaining heat after expansion to heat the boiler feed water, but also to heat the air that is to be introduced into the boiler for combustion purposes.
Oftentimes it is customary in boilers, whether they be fire tube boilers, water tube boilers, or any configuration, to take the fluid which has been expanded and later condensed, and heat it from the energy of the exhaust gas that is normally being exhausted. This is accomplished in a number of different ways. However, to date low pressure boiler systems such as fire tube boilers and related types have not incorporated effective heat exchangers. This is due to the fact that oftentimes the heat exchangers provided too much back pressure to such low pressure boilers. They thereby created blockages and the inability of the boiler to function under its normal interior fire wall pressures.
In other words, boilers oftentimes function with an interior pressure of no more than plus point zero 0.05 pressure in inches of water. When the back pressure is increased the walls and other elements of the boiler are not sufficient to withstand such back pressure and the boiler leaks and does not function effectively.
Another problem which has plagued economizer designs and heat recovery heat exchangers, has been the problem related to proper orientation of heat exchanger elements. The size of the heat transfer plates or fins, and tubes, or other materials in which the fluid is carried, has not been optimally sized. In other words, the size of the conduit or heat exchange element in which the fluid or material that is to be carried is not sized with respect to the heat transfer plates or fins.
In the given relationships between a gas transferring heat to a fluid within a conduit having heat exchange plates, the relationship of the conduit and the plates in order to pick up the heat of the gas, should be optimized. This invention enables an establishment of that relationship between the plates and conduit in order to optimize heat transfer between fluids of various types by proper heat or plate relationships and corresponding tube size. This invention optimizes the relationship between the heat transfer elements so that when a fluid passes with respect to another fluid, such as a liquid in a tube having fins or plates passing in relationship to a gas on the outside of the tube, the surface area design of the plates are optimized to enhance the flow of heat between the respective fluids.
In addition to the foregoing features of this invention, this specification teaches improved swaging between a resilient metal tube, such as stainless steel, and a deformable metal plate, such as one of copper or aluminum. When certain resilient metals such as steel are expanded into deformable materials, such as aluminum or copper, the deformation remains. Thus, the tightened swaged relationship between the two metals cannot be maintained. This is particularly serious when contact pressures must be maintained to provide heat transfer.
This invention has overcome the prior art difficulty by enabling a resilient metal, such as the stainless steel tube, to be expanded against a deformable metal, such as the aluminum plates. This is accomplished by having a deformable sleeve receive the resilient tube therein by having it driven or pulled therethrough to deform the sleeve against the plate surrounding the sleeve, thereby allowing a close fit with the resilient tube pressed against the inside diameter of the sleeve and the sleeve pressed against and deformed or swaged against the plate.
In essence, this invention incorporates an enhanced ability to utilize exhaust gases for heating fluid that is to be used as boiler feed water. It provides a superior design of plate to tube relationship to optimize the heat transfer between two fluids. In addition thereto, a superior means for connecting the tubes and the plates is provided for enhanced contact pressure with attendantly improved heat transfer.